Conventionally, in a lithography process which is a process in manufacturing a semiconductor device, various exposure apparatuses are used to transfer a circuit pattern formed on a mask or a reticle (hereinlater, generically referred to a “reticle”) onto a substrate such as a wafer, or glass plate or the like that is coated with a resist (photoresist).
For example, with the exposure apparatus for semiconductor devices, reduction projection exposure apparatuses that reduce and transfer the pattern formed on a reticle using a projection optical system are mainly used, so as to accomplish the finer minimum line width (device rule) of the pattern required with higher integration of integrated circuits.
Of the reduction projection expose apparatuses, the static type exposure apparatus (so-called stepper) which employs a step-and-repeat method to sequentially transfer the pattern formed on the reticle to a plurality of shot areas on the wafer, or an improved stepper which is the scanning exposure apparatus that employs a step-and-scan method (so-called scanning stepper) disclosed in, for example, Japanese Patent Laid Open No. 08-166043, which synchronously moves the reticle and the wafer in a one-dimensional direction and transfers the retile pattern onto each shot area on the wafer, are well-known.
In these reduction projection exposure apparatuses, a base plate which is to be the base of the apparatus, is first of all, arranged on a floor surface. On the plate, a main column which supports a reticle stage, a wafer stage, and a projection optical system (projection lens) and the like, is arranged via a variation isolator bed which is arranged to isolate a vibration of the floor. With recent reduction projection exposure apparatuses, as the vibration isolator bed, an active vibration isolator bed is employed. The active vibration isolator bed comprises: an air mount of which the internal pressure is adjustable; and an actuator such as a voice coil motor. And, the vibration of the main column is suppressed by controlling the voice coil motor and the like based on measurement values of six accelerometers attached to the main column (mainframe).
With the steppers, after a shot area on the wafer is exposed, exposure is sequentially repeated onto the remaining shot areas. Therefore, a reaction force due to the acceleration and deceleration of the wafer stage (in the case of the stepper) or the reticle stage and the wafer stage (in the case of the scanning stepper) is a factor of vibration of the main column, which in turn caused an unfavorable situation such as creating a positional relationship error between the projection optical system and the wafer.
The error in the positional relationship on alignment and on exposure has consequently been the cause of the pattern being transferred onto a position on the wafer different from a designated value, or in the case in which the positional error includes a vibration component, led to an image blur (increase in the pattern line width).
Accordingly, in order to prevent the pattern being transferred from shifting, or to suppress the image blur, the vibration of the main column needed to be sufficiently damped by the above active vibration isolator bed. For example, in the case of the stepper, alignment operation and exposure operation are to begin after the wafer stage is positioned at a desired place and is sufficiently settled down, whereas in the case of the scanning stepper, the reticle stage and the wafer stage has to be sufficiently settled in synchronous before exposure is performed. Consequently, there are factors of lowering throughput (productivity).
To solve such inconvenience, as disclosed in Japanese Patent Laid Open No. 08-166475, etc., it is known that the reaction force to be generated by movement of the wafer stage is mechanically released to the floor (the earth) by using a frame member. Also, as disclosed in Japanese Patent Laid Open No. 08-330224, etc., it is known that the reaction force to be generated by movement of a reticle stage is mechanically released to the floor (the earth) by using a frame member.
With the increase in size of the wafer in recent yeas, the size of the wafer stage has also increased, making it difficult to secure the throughput to some extent and perform precise exposure even by using the invention disclosed in Japanese Patent Laid Open No. 08-166475 or 08-330224, etc. earlier described. To be more specific, the frame member itself vibrates due to a reaction force which is released to the floor side through the frame member and, on the contrary, this vibration becomes a factor of deterioration in positional controllability of a stage. Also, the reaction force released to the floor might be transmitted to a main column (main body) holding a projection optical system through a vibration isolator, etc. and this might result in a vibration of the main column.
Since the device rule will become finer in the future, and the wafer and the reticle larger in size, it is evident that the vibration caused when the stage is driven will become a more serious problem. Accordingly, the requirement of a new technology to be developed is pressing, to effectively suppress the adverse effects of the vibration of each component affecting the exposure accuracy. Precision machines other than the exposure apparatus also have the similar problem.
The present invention has been made in consideration of the situation described above, and it is the first object of the present invention to provide a stage unit capable of improving positional controllability of a stage by suppressing an influence of a reaction force generated by driving the stage.
Also, the present invention has as its second object to provide an exposure apparatus capable of improving exposure precision and throughput by suppressing an influence on the exposure accuracy exerted by vibrations of components in the apparatus.
Further, the present invention has as its third object to provide a device manufacturing method capable of improving the productivity of electron devices with high integration.